Abstract
We report the impact of oxygen (O2) plasma time on an amorphous indium–gallium–zinc oxide (a-IGZO) thin-film surface that was carried out before TEOS deposition in order to optimize the performance of thin-film transistors (TFTs). TheO2 plasma time of 60 s possessed the largest on/off current ratio of >108, with a field-effect mobility (µFE) of 8.14 cm2 V−1 s−1, and the lowest subthreshold swing (S.S.) of 0.395 V/decade, with a threshold voltage (Vth) of −0.14 V. However, increases in Ioff and S.S. and decreases in the µFE were observed for the longer O2 plasma time of 120 s. As the O2 plasma time increased, the reduction in the carrier concentration in the IGZO channel layer may have resulted in an increase in Vth for the IGZO TFT devices. With an increase in the O2 plasma time, the surface roughness of the IGZO channel layer was increased, the carbon content in the TEOS oxide film was reduced, and the film stoichiometry was improved. The SIMS depth profile results showed that the O/Si ratio of TEOS oxide for the sample with the O2 plasma time of 60 s was 2.64, and its IGZO TFT device had the best electrical characteristics. In addition, in comparison to the IGZO TFT device without O2 annealing, larger clockwise hysteresis in the transfer characteristics revealed that a greater number of electrons were trapped at the interface between TEOS oxide and the a-IGZO channel layer. However, hysteresis curves of the O2-annealed IGZO TFTs with various O2 plasma times were greatly reduced, meaning that the electron traps were reduced by O2 annealing.
Highlights
Due to fast advances in optoelectronic technology, the generation of displays will have thinner, lighter, and bigger screens
Liu et al recently reported [17] on IGZO thin films that were treated with an Ar/O2 plasma combination with various oxygen content ratios, resulting in the bottom-gate IGZO thin-film transistors (TFTs) have improved device operation characteristics
The results were ascribed to passivating the interfacial and bulk traps by reducing the oxygen vacancies. This was the first study to our knowledge that focused on the effects of the O2 plasma treatment prior to the tetraethyl–orthosilicate (TEOS) oxide gate dielectric deposition and O2 annealing on the electrical characteristics of top-gate IGZO TFTs, wherein the compositions of TEOS oxide interfaces with amorphous indium– gallium–zinc oxide (a-IGZO) films were reported
Summary
Due to fast advances in optoelectronic technology, the generation of displays will have thinner, lighter, and bigger screens. Jeong et al [14] reported that O2 plasma treatment on the a-IGZO channel layer decreases the oxygen vacancy density of the IGZO films at low processing temperatures, improving the IGZO channel layer material and the performance of IGZO TFT devices. Liu et al recently reported [17] on IGZO thin films that were treated with an Ar/O2 plasma combination with various oxygen content ratios, resulting in the bottom-gate IGZO TFTs have improved device operation characteristics. The results were ascribed to passivating the interfacial and bulk traps by reducing the oxygen vacancies Most notably, this was the first study to our knowledge that focused on the effects of the O2 plasma treatment prior to the tetraethyl–orthosilicate (TEOS) oxide gate dielectric deposition and O2 annealing on the electrical characteristics of top-gate IGZO TFTs, wherein the compositions of TEOS oxide interfaces with a-IGZO films were reported. The best μFE of 8.14 cm V−1s−1, S.S. of 0.395 V/decade, Vth of −0.14 V, and lower ∆Vth of 0.5 V from the hysteresis curve were obtained in the IGZO TFTs that had been subjected to O2 plasma treatment for 60 s and O2 annealing
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